Work will be carried out to see if increased extracellular (K+) augments the rate of protein synthesis in the guinea pig cortex in situ. (We have already demonstrated that it does so in vitro). Two holes will be made in the skull of a guinea pig, one on each side of the mid-line. The dera will be perforated and plastic cups glued around the holes. By filling the plastic cups with buffers of different compositions the underlying cortex will be exposed to differet ionic and chemical environments. The effect of these environments upon protein syntesis will be assessed by injecting the animal with 3H-lysine and measuring its incorporation into protein in the cortical region below each chamber. Experiments will be carried out to determine whether veratrine inhibition of protein synthesis is confined to neurons. Autoradiography at the light microscope level will be carried out upon hippocampal slices exposed to 3H-lysine in the presence or absence of veratrine. Micrographs will be examined with the aim of measuring the effect of veratrine on incorporation into neurons and into glia. Experiments will be carried out to further study the basis for the differential sensitivity of brain tissue protein synthesis to extracellular K ion. Effects of extracellular K ion and ouabain upon synthesis, ATP levels, and intracellular K ion, Na ion concentration will be compared in brain and non-nervous tissue. The purpose is to determine whether the effect of altered cell K ion/N ion ratios upon synthesis is confined to cerebral tissue.